Cellulose and lignin are two of the most prominent renewable carbon sources. These two biomolecules are found together in lignocellulosic materials which include all vascular plants. Lignocellulosic materials are domestically renewable and becoming increasingly valuable a feedstock since petroleum feedstocks have become more expensive and more reliant on imported sources.
Lignin comprises roughly 25% of lignocellulosic biomass. It is formed in plants primary by polymerization of three precursors which forms cross-linked macromolecules with molecular masses in excess of 10,000. Because lignin polymerizes within itself and with the other cell wall components, it minimizes the accessibility of cellulose and hemicellulose to microbial enzymes. In its polymerized form, lignin is generally associated with reduced digestibility of the overall plant biomass, which helps defend against pathogens and pests but which hinders its commercial value.